st: Overidentifying test

Hi,
How do I test the over identifying restriction test in Stata? Do I need to
install anything?
I have used these commands but it doesn't seem to be working.
First I estimate a 2SLS estimation with two instrumental variable: twoboys and
twogrils. This gives me single over identifying restriction.
ivreg workedm (morekids=twoboys twogirls) agem1 agefstm boy1st black hispan o
thrace
Then to test I use these two commands. The error message that I get is under
each commands.
*sc install overid
variable install not found
no variables defined
r(111);
overid
unrecognized command: overid
r(199);
--
Tharshini THANGAVELU
Forskarbacken 8 / 101
114 16 Stockholm
Sweden
Phone +46 (0)735 53 43 90
E-mail thth4658@student.su.se
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